1. Field of the Invention
The present invention relates to communications, and more particularly, to a method of tuning a frequency and apparatus thereof. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for a communications device.
2. Discussion of the Related Art
Generally, an analog frequency tuning device employs an inductor or capacitor system.
FIG. 1A and FIG. 1B are circuit diagrams of analog tuning devices according to a related art, respectively.
Referring to FIG. 1A, a variable-inductor analog frequency tuning device is shown.
Referring to FIG. 1B, a variable-capacitor analog frequency tuning device is shown.
In the above-explained two kinds of systems, a user performs tuning by directly manipulating an external adjustment button for adjusting a variable inductor L or a variable capacitor C.
To tune a frequency of another channel after tuning a frequency corresponding to one channel using an external adjustment button, a user needs to adjust frequencies using the external adjustment button again.
In case that there are a plurality of channels to be used by a user, the external adjustment button needs to be manipulated each time a frequency corresponding to each of the channels is changed.
And, it is difficult for a user to remember the frequencies corresponding to a plurality of the channels, respectively.
Moreover, a user needs to finely manipulate the adjustment button for frequency tuning.
FIG. 2 is a block diagram of a digital frequency tuning device according to a related art.
Referring to FIG. 2, a digital frequency tuning device according to a related art consists of a reference frequency oscillator 1, a voltage controlled oscillator (VCO) 2, a divider 3, a phase detector 4 and a pulse voltage converter 5.
The reference frequency oscillator 1 outputs a reference frequency.
The voltage controlled oscillator (VCO) 2 adjusts to output an oscillation frequency according to an input voltage.
The divider 3 divides an output (oscillation frequency) of the voltage controlled oscillator 2 by a predetermined ratio.
The phase detector 4 compares an output of the reference frequency oscillator 1 to an output of the divider 3 and then outputs a corresponding difference between the two outputs.
The pulse voltage converter 5 converts an output of the phase detector 4 to a voltage and then outputs the voltage to the voltage controlled oscillator 2.
In case of using the related art digital frequency tuning device, a user presses a frequency setting number button to input a specific frequency in direct.
Besides, the user inputs to designate the specific frequency and makes the designated frequency correspond to several numbers to store in a memory. Thereafter, if a button of a predetermined number is pressed, the frequency corresponding to the pressed number is tuned. Hence, a frequently usable frequency can be simply tuned by pressing the corresponding number button.
Yet, since it is difficult to memorize the entire frequencies corresponding to the numbers, respectively, each number button needs to be pressed one by one to find a specific frequency. For instance, a frequency corresponding to a button No. 5 is stored as 95.9 MHz and a current device is set to a frequency corresponding to a button No. 1. If a user is unable to remember that the button No. 5 is set to 95.9 MHz, it is highly probable that the user tries to press other buttons No. 2, No. 3, No. 4 and the like. Finally, the user can find 95.9 MHz of No. 5 after having tries various different number buttons.
Thus, in the related art device using the analog or digital frequency tuning, it is difficult to perform the frequency tuning.